Method and apparatus for reproducing audio signals at various speeds by dividing original audio signals into a sequence of frames based on zero-cross points

ABSTRACT

In a method of reproducing audio signals of the present invention, audio reproducing speed can be changed without changing tone and quality of audio signals. Audio signals are filtered to extract basic audio signals. Zero-cross points in the basic audio signals are detected. The original audio signals are divided into a plurality of frames on the basis of the zero-cross points on a time axis. The frames are thinned out, and the original audio signals are reproduced as voice on the basis of the frames left so as to accelerate reproducing speed. On the other hand, the original audio signals are reproduced by repeating the frame so as to make reproducing speed slower.

This application is a divisional of application Ser. No. 08/827,909,filed on Apr. 7, 1997, now U.S. Pat. No. 6,026,061 the entire contentsof which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a method of reproducing audio signalsand an audio player, more precisely relates to a method of reproducingaudio signals which have been recorded on a recording medium, such ase.g., a compact disk (CD), as voice, and an audio player employing saidmethod.

In some cases, the audio reproducing speed of an audio player, such as,a CD player, a tape recorder or, a video player, must be slower orfaster than the normal reproducing speed. For example, the reproducingspeed is accelerated when a listener wants to listen the recorded audiodata in a short time. On the other hand, the reproducing speed is madeslower if the audio data was rapidly recorded.

Conventionally, the rotational speed of a CD or running speed of a tapeis changed to change the reproducing speed of the audio player.

By the conventional method of changing the reproducing speed, frequencyof the audio signals, which have been read from the recording medium,e.g., the CD, is also changed according to the change of the reproducingspeed, so that the tone of the reproduced voice is changed and.

A conventional method of changing the reproducing speed while keepingthe original tone will be explained with reference to FIG. 8. Originalaudio signals (a) are divided into a plurality of frames (A1, A2, A3,A4, A5, A6 . . . ), each of which has fixed time length (t). The audioreproducing speed can be changed by selecting the frames (A1, A2, A3,A4, A5, A6 . . . ). To reproduce audio signals twice as fast as thenormal reproducing speed, for example, the frames (A1, A2, A3, A4, A5,A6 . . . ) are partially thinned out, and the audio signalscorresponding to the frames left, e.g., the frames (A1, A3, A5 . . . ),are reproduced as voice. By this method, reproducing time of reproducedaudio signals (c) can be half of original recording time. Namely, thelistening time can be reduced to half. Further, frequency of theoriginal audio signals (a) or cycle time (T) thereof is not so changed.Consequently, the audio signals (a) can be reproduced as the voice withoriginal tone.

If the audio signals corresponding to the selected frames (A1, A3, A5 .. . ) are merely connected, the signals are not met in connectingsections (B1, B2, B3, B4) as shown audio signals (b), and uncomfortablenoise is produced in each connecting section (B1, B2, B3, B4).

To reduce the noise, the signal level at an end point of one selectedframe, e.g., the frame (A1), and signal level at a starting point of anadjacent selected frame, e.g., the frame (A3), are functionallycoincided each other. An example of functional formula is,

W(n)=0.5-0.5 cos (2 πn/M)

n: signal level in the frame; and

M: n=0, 1, . . . M.

By this process, the original audio signals (a) can be formed into audiosignals (c) which are continuous of the connecting sections (B1, B2, B3,B4), so that the uncomfortable noise in the reproduced audio signals(voice) can be reduced.

However, the conventional method has following disadvantages.

In the conventional method, the signal level of the original audiosignals (a) in the connecting sections (B1, B2, B3, B4) must be changedto a prescribed level, e.g., zero, so the cycle time of the changedaudio signals (c) in some connecting sections are quite different fromthat of the original audio signals (a). If the cycle time of the changedaudio signals (c) is partially quite different from that of the originalaudio signals (a), the tone of the reproducing audio signals (voice) isquite different from the original voice. Further, the frequency of thereproduced audio signals (c) corresponding to the connecting sections(B1, B2, B3, B4) is also different from the original audio signals (a),so quality of sound or voice decreases.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of reproducingaudio signals, which is capable of changing the audio reproducing speedwithout changing the tone and the quality of audio signals. Anotherobject is to provide an audio player employing such a method.

To achieve the objects, the present invention has following structures.

The first basic structure of the method comprises the steps of:

filtering original audio signals, which have been recorded on arecording medium, to extract basic audio signals;

detecting zero-cross points in the basic audio signals;

dividing the original audio signals into a plurality of frames on thebasis of the zero-cross points on a time axis; and

thinning out the frames; and

reproducing the original audio signals on the basis of the frames leftso as to accelerate reproducing speed.

The second basic structure of the method comprises the steps of:

filtering original audio signals, which have been recorded on arecording medium, to extract basic audio signals;

detecting zero-cross points in the basic audio signals;

dividing the original audio signals into a plurality of frames on thebasis of the zero-cross points on a time axis; and

reproducing the original audio signals by repeating the frame so as tomake reproducing speed slower.

The first basic structure of the audio player comprises:

a filtering section filtering original audio signals, which have beenrecorded on a recording medium, to extract basic audio signals;

a detecting section detecting zero-cross points in the basic audiosignals; and

a signal processing section dividing the original audio signals into aplurality of frames on the basis of the zero-cross points on a timeaxis, thinning out the frames, and reproducing the original audiosignals on the basis of the frames left so as to accelerate reproducingspeed.

The second basic structure of the audio player comprises:

a filtering section filtering original audio signals, which have beenrecorded on a recording medium, to extract basic audio signals;

a detecting section detecting zero-cross points in the basic audiosignals; and

a signal processing section dividing the original audio signals into aplurality of frames on the basis of the zero-cross points on a timeaxis, and reproducing the original audio signals by repeating the frameso as to make reproducing speed slower.

In the present invention, the zero-cross points may be included inrising parts or in trailing parts of the basic signals.

In the method and the audio player of the present invention, the cycletime of the reproduced audio signals (voice) corresponding to theconnecting sections between the frames is the same as that of the basicaudio signals, and the signals are smoothly connected in the connectingsections. Thus, the audio signals can be reproduced without changing thetone and the quality of audio signals even if the original audio signalsare reproduced on the basis of the frames left so as to acceleratereproducing speed, or reproduced by repeating the frame so as to slowreproducing speed.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way ofexample and with reference to the accompanying drawings, which are givenby way of illustration only, in which:

FIG. 1 is an explanation view showing a basic idea of the audioreproducing method of the present invention;

FIG. 2 is a block diagram of an audio player of an embodiment of thepresent invention;

FIG. 3 is a block diagram of an arithmetic unit shown in FIG. 2;

FIG. 4 is a flow chart showing the opening steps performed by the audioplayer shown in FIG. 2, wherein original audio signals in a main frameare voice;

FIG. 5 is a flow chart showing the operating steps of the audio playershown in FIG. 2, wherein original audio signals in the main frame arenot voice;

FIG. 6 is an explanation view showing a process of the case shown inFIG. 4;

FIG. 7 is an explanation view showing a process of the case shown inFIG. 5; and

FIG. 8 is an explanation view showing a process of the conventionalaudio player.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

A preferred embodiment of the present invention will now be described indetail with reference to the accompanying drawings.

First the basic idea of the method of reproducing audio signals of thepresent invention will be explained with reference to FIG. 1.

Sounds include: voiced sounds, e.g., vowel sounds, having cyclical waveforms and being generated by vibration of vocal cord; and unvoicedsounds, e.g., constant sounds [s], being generated by air flow passingthrough narrow spaces in the mouth without vibrating the vocal cord. Ifthe voiced sounds are not mutually continuous in the connecting sections(B1, B2, B3, B4) of the frames (see FIG. 8), uncomfortable sounds(noise) are heard. On the other hand, even if the unvoiced sounds arenot mutually continuous therein, less uncomfortable sounds are heardbecause the frequency of the unvoiced sounds are quite higher than thefrequency of the voiced sounds (equal to the vibration frequency of thevocal cord: about 70-350 Hz). With this facts, even if the audio signalsare reproduced as voice while thinning out the frames (A1, A2, A3, A4,A5, A6 . . . ) to accelerate the reproducing speed or repeating framesto make the reproducing speed slower, the tone, the sound level and thequality of sounds can be maintained by continuing voiced sounds in theconnecting sections (B1, B2, B3, B4).

In the method of reproducing the audio signals, basic audio signals (d),which have basic frequency Fp and basic cycle time TP, are extractedfrom original audio signals (a) by low-pass filtering. Zero-cross points(D) in rising parts or trailing parts of the basic signals (d) aredetected. In FIG. 1, the zero-cross points (D) in the rising parts areshown. The zero-cross points (D) are shown as black circles on a timeaxis. The original audio signals (a) are divided into a plurality offrames (C1, C2, C3, C4, C5, C6), each of which has time length of 4×Tp.

In the case that the frames (C1, C2, C3, C4, C5, C6) are partiallythinned out, e.g., skipping every second frame, to accelerate thereproducing speed, or that each frame (C1, C2, C3, C4, C5, C6) isrepeated once or more to make the reproducing speed slower, reproducedaudio signals (e) can be always continuous at the zero-cross points (D)in the connecting sections between the frames without adjusting signallevels. FIG. 1 shows the case of partially thinned out the frames (C1,C2, C3, C4, C5, C6) by skipping every second frame (C2, C4) toaccelerate the reproducing speed, so the reproduced audio signals (e)are smoothly continued at the zero-cross points (D) in the connectingsections between the selected frames (C1, C3, C5). Further, since thezero-cross points (D) must be included in the rising parts (the caseshown in FIG. 1) or the trailing parts of the basic signals (d), phasesof the reproduced audio signals (e) are not inverted in the connectingsections, so that the reproduced audio signals (e) corresponding to theframe ((C1, C3, C5) left can be smoothly continued.

By the above-described method, the frequency of the reproduced audiosignals (e) corresponding to the connecting sections between the framesis highly shifted from the basic frequency fp and the reproduced audiosignals (e) can be continued in the connecting sections. Therefore, thetone and the quality of the reproduced audio signals (voice and sounds)cannot be kept. Note that, the basic signals (d) in the connectingsections are shown in FIG. 1 for explanation purposes, but thereproduced audio signals (e) are actually constituted by the originalaudio signals (a) corresponding to the selected frames (C1, C3, C5).

As described above, FIG. 1 shows the case of accelerating thereproducing speed faster than the normal speed. On the other hand, tomake the reproducing speed slower than the normal reproducing speed, theoriginal audio signals (a) of the frames (C1, C2, C3, C4, C5, C6) arecontinuously reproduced by repeating each frame (C1, C2, C3, C4, C5, C6)once or more. For example, the original audio signals (a) may bereproduced as following order: C1, C1, C2, C2, C3, C3, C4, C4, C5, C5,C6, C6. By this example, the original audio signals (a) can bereproduced 0.5 time as fast as the normal reproducing speed. If theoriginal audio signals (a) are reproduced by the order of C1, C1, C2,C3, C4, C4, C5, C6, the original audio signals (a) can be reproduced0.75 time as fast as the normal reproducing speed.

Next, the audio player employing the above described method will beexplained with reference to FIGS. 2-7. Note that an audio reproducingcircuit 10 of a CD-ROM book, which is an example of the audio player,will be explained, but magnetic tapes, flexible disks, IC cardsincluding semiconductor memories, e.g., RAM, etc. may employed asrecording media. Original audio signals (a), which are voice signalsreading a story, are recorded on a CD as PCM data, which have beensampled at a prescribed sampling frequency.

The audio reproducing circuit 10 will be explained with reference toFIGS. 2 and 6.

The PCM data is read from the CD 14 by a reading section 12, whichincludes an optical pick-up, and inputted to the audio reproducingcircuit 10.

The PCM data read by the reading section 12 is stored in an input-memory16 in order.

An arithmetic unit 18 (a microprocessor) reads a prescribed amount ofthe PCM data, which equals the amount of data of a main frame (E), fromthe input-memory 16 in the order of storing, and stores them in anarithmetic-memory 20. The arithmetic unit 18 extracts the basic audiosignals (d), which have the basic frequency Fp (slightly changedaccording to voice), from the original audio signals (a) of one mainframe (E). Then the arithmetic unit 18 detects the zero-cross points (D)in the rising or the trailing parts of the basic audio signals (d). Theoriginal audio signals (a) of the main frame (E), which have been storedin the arithmetic-memory 20, are divided, by the zero-cross points onthe time axis, into a plurality of sub frames (C1-C11). When thereproducing speed (f) is inputted by a control unit 22 (amicroprocessor), if the reproducing speed(f) is faster than the normalreproducing speed, the arithmetic unit 18 thins out the sub frames(C1-C11) to omit a proper number of the sub frames, then the arithmeticunit 18 reads the data corresponding to the selected sub frames (subframes left) from the arithmetic-memory 20 and stores the data in anoutput-memory 24 in order. On the other hand, if the reproducing speed(f) is slower than the normal reproducing speed, the arithmetic unit 18repeats proper sub frames once or more, then the arithmetic unit 18reads the data from the arithmetic-memory 20 according to the repeatingorder of the sub frames and stores the data in the output-memory 24 inorder. The PCM data stored in the output-memory 24 will constitute thereproducing audio signals (e).

DAC (Digital to Analogue Converter) 26 continuously reads the data ofthe original audio signals (a) corresponding to the sub frames from theoutput-memory 24 at fixed speed. The data read is converted intoanalogue signals, and they can be reproduced as the reproduced audiosignals (e) at the assigned reproducing speed (f). The reproduced audiosignals (e), which have been outputted from the DAC 26, are outputtedfrom a speaker (not shown) as voice.

Note that, the control unit 22 assigns the reproducing speed (f) to thearithmetic unit 18. Control programs for the the arithmetic unit 18 arestored in a flush memory 28. Capacity of the input-memory 16 and theoutput-memory 24 are designed according to processing speed of thearithmetic unit specifically the memories 16 and 24 do not become emptyor full while operating. A memory space of one memory unit may bedivided as the memories 16, 20 and 22.

The arithmetic unit 18 will be explained with reference to FIGS. 3-7.

A filtering section (digital filtering section) 30 filters the PCM dataof the original audio signals (a) by low-pass filters to remove unvoicedparts, so the basic audio signals (d), whose basic frequency is Fp(about 70-350 Hz), can be extracted. In the present embodiment, a coupleof IIR-type low pass filters are employed, and their cut off frequencyis 200 Hz (the middle frequency of the basic frequency 70-350 Hz). Byusing this filters, the basic audio signals (d) having the basicfrequency Fp and the basic cycle time Tp (see FIGS. 1, 6 and 7) areoutputted from the filtering section 30.

A detecting section 32 detects the zero-cross points (D), which areincluded in the rising (or the trailing) parts of the basic audiosignals (d), of each main frame (E). In the present embodiment, thezero-cross points (D) in the rising parts of the basic audio signals (d)are detected. The detecting section 32 divides the basic audio signals(d) of one main frame (E), by the zero-cross points (D), into aplurality of sub frames (C1, . . . Cn; "n" being a natural number), andeach sub frame (C1, . . . Cn) has a prescribed time length, which is aprescribed times as long as the basic cycle time Tp. The detectingsection 32 outputs address data of the connecting sections between theadjacent sub frames, e.g., a position from a starting point of the subframe, which is stored in the arithmetic-memory 20 as zero-cross data(g).

A voice detecting section 34 detects if the detecting section 32 detectsthe zero-cross points (D) or not. When the detecting section 32 detectsno zero-cross point (D), the voice detecting section 34 outputs no-voicesignals (h), which indicate unvoiced sounds or that no voice isrecorded. Note that, the detecting section 32 may output the no-voicesignals (h) instead of the voice detecting section 34.

A signal processing section 36 defines the reproducing speed (f) whenthe control unit 22 assigns the reproducing speed (f). Namely, thereproduced audio signals (e) are reproduced at the assigned speed, whichis f ("f" is a positive real number) times as fast as the normalreproducing speed. In the case of detecting the zero-cross points (D) inthe main frame (E), the action of the signal processing section 36 isdifferent from that in the case of detecting no zero-cross points (D).

First the case of detecting the zero-cross points (D), namely the casethat no no-voice signals (h) are sent from the voice detecting section34 will be explained.

As shown in FIG. 4, the signal processing section 36 counts a number ofthe sub frames (C1, . . . Cn) on the basis of the zero-cross data (g)and reads the original audio signals (a) from the arithmetic-memory 20.The signal processing section 36 selects one sub frame out of everygroup of the sub frames, in which the sub frames of number "f" (anatural number) are included, on the basis of a predetermined rule (STEPS100). The original audio signals (a) of the selected sub frames arestored in the output-memory 24 (STEP S102); the original audio signals(a) of the non-selected (skipped or thinned out) sub frames are notstored (STEP S104). Note that, to continuously reproduce the audiosignals (voice), the original audio signals (a) corresponding to theselected sub frames are stored in the output-memory 24 in the form ofthe reproduced audio signals(e).

The signal processing section 36 detects if any sub frames are left inthe main frame (E) stored in the arithmetic-memory 20 or not (STEPS106). If there is a sub frames left in the main frame (E), the signalprocessing section 36 reads the sub frame left (STEP S108) and returnsto STEP S100. On the other hand, if there are no sub frames left in themain frame (E), the signal processing section 36 stops processing theoriginal PCM data (a) of the main frame (E) stored in thearithmetic-memory 20. Note that, in the case that there is a remainder(I), whose length is shorter than the cycle time Tp, at the end of themain frame (E), the remainder (I) is stored in the arithmetic memory 20,and the remainder (I) will be added to next main frame (E). Namely,length of the remainder (I) is added to the length of the next mainframe (E).

Upon completing to process the PCM data of the original audio signals(a) of the main frame (E) stored in the arithmetic-memory 20, thearithmetic unit 18 reads the PCM data of the next main frame (E) fromthe input-memory 16 and stores this data in the output-memory 20, thenrepeats the above described flow process.

Specific examples will be explained with reference to FIG. 6. In thisexample, the reproducing speed (f) is assigned to two (f=2), so thereproduced audio signals (e) are reproduced at the reproducing speedtwice as fast as the normal reproducing speed. The signal processingsection 36 counts the number of the sub frames (C1, . . . C11) from thefirst sub frame (C1). The signal processing section 36 selects one subframe out of every group of the sub frames, in which two sub frames areincluded. The original audio signals (a) of the selected sub frames(shown as slashed area) are read from the arithmetic-memory 20 andstored in the output-memory 24 in order. The signal processing section36 processes all main frames as well. With this action, the amount ofthe PCM data of the reproduced audio signals (e) in the output-memory 24is made half, so the audio data (e) can be reproduced at the reproducingspeed twice as fast as the normal reproducing speed.

In the case of "f"=1.5, namely the assigned reproducing speed is 1.5time as fast as the normal reproducing speed, the signal processingsection 36 selects two sub frames out of every group of the sub frames,in which three sub frames are included. The original audio signals (a)of the selected sub frames (shown as slashed area) are read from thearithmetic-memory 20 and stored in the output-memory 24 in order. Withthis action, the amount of the PCM data of the reproduced audio signals(e) in the output-memory 24 is made 2/3, so the audio data (e) can bereproduced at the reproducing speed 1.5 time as fast as the normalreproducing speed.

In the case of "f"=1, the signal processing section 36 selects one subframes out of every group of the sub frame, in which one sub frame isincluded. Namely, every sub frame is selected, so the original audiosignals (a) of all sub frames (C1-C11) are read from thearithmetic-memory 20 and stored in the output-memory 24. Thus, the audiodata (e) can be reproduced at the normal reproducing speed.

Cases of "f"≧1 have been described above. If "f"<1, namely thereproducing speed is made slower, each sub frame or selected sub framesare repeated so as to make the amount of the PCM data of the reproducedaudio signals (e) in the output-memory 24 as 1/f time as that of the PCMdata of the main frame (E). Thus, the reproducing speed (f) can be madeslower than the normal reproducing speed.

The example of slower reproducing speed will be explained with referenceto FIG. 6. In the case of "f"=0.75, namely the assigned reproducingspeed is 0.75 time as fast as the normal reproducing speed, the signalprocessing section 36 counts the number of the sub frames and reads theoriginal audio signals (a) of each sub frame. The signal processingsection 36 selects one sub frames out of every three sub frames andrepeats to read the signals (a) of the selected sub frame. The originalaudio signals (a), which have been read and repeated by the signalprocessing section 36, are sequentially stored in the output-memory 24in the read-and-repeat order. This process will be executed for all mainframes (E). With this action, the amount of the PCM data of thereproduced audio signals (e) in the output-memory 24 is made 4/3(=1/0.75), so the audio data (e) can be reproduced at the reproducingspeed 0.75 time as fast as the normal reproducing speed. Namely, in thisexample, the original audio signals (a) of the selected sub frames (C1,C4, C7, C10), shown as black area, are repeated twice.

In some cases, depends on the value "f", the amount of the data in themain frame (E) does not match with that of the data in the output-memory24. A value "(the amount of the data in the main frame)/(the data in theoutput-memory)"is made close to the assigned value "f" by selecting(thinning out) or repeating the sub frames.

Next, the case in which no zero-cross points are detected and theno-voice signals (h) are sent from the voice detecting section 34 willbe explained.

As shown in FIG. 5, if "f"≧1, "(number of the samples of the PCM data inone main frame)/f" (a positive integer) of the PCM data in the mainframe (E) are read from the starting point of the main frame (E) andsequentially stored in the output-memory 24 in that order. With thisprocess, the amount of the PCM data of the reproduced audio signals (e)of the main frame (E) in the output-memory 24 is made 1/f, so the audiosignals (e) can be reproduced at the speed "f" times as fast as thenormal reproducing speed.

A concrete example is shown in FIG. 7. When "f=2" is inputted, thereproducing speed is assigned to twice as fast as the normal reproducingspeed. The signal processing section 36 reads 1/2 of the samples of thePCM data in the main frame (E) and sequentially stores the PCM data,which have been read, in the output-memory 24. With this process, theamount of the PCM data of the reproduced audio signals (e) of the mainframe (E) in the output-memory 24 is made 1/2, so the audio signals (e)can be reproduced at the speed twice as fast as the normal reproducingspeed. In the case of "f=1.5" too, the signal processing section 36processes the data by the same manner.

If "f"<1, "(number of the samples of the PCM data in one mainframe)/f)-1" (a positive integer) of the samples of the PCM data in themain frame (E) are read from the starting point of the main frame (E)and sequentially stored in the output-memory 24 in that order. Then allPCM data in the main frame (E) are sequentially stored therein. Withthis process, the amount of the PCM data of the reproduced audio signals(e) of the main frame (E) in the output-memory 24 is made 1/f (f<1), sothe audio signals (e) can be reproduced at the speed "f" (f<1) times asslow as the normal reproducing speed.

A concrete example is shown in FIG. 7. When "f=0.75" is inputted, thereproducing speed is assigned to 0.75 times as slow as the normalreproducing speed. The signal processing section 36 reads"1/0.75-1(=1/3)", of the samples of the PCM data in the main frame (E)and sequentially stores the PCM data, which has been read, in theoutput-memory 24. Then all PCM data in the main frame (E) issequentially stored therein. With this process, the amount of the PCMdata of the reproduced audio signals (e) of the main frame (E) in theoutput-memory 24 is made 4/3 (=1/3+1=1/f), so the audio signals (e) canbe reproduced at the speed 3/4 (f) time as slow as the normalreproducing speed.

If main frames (E), in which no sounds are included, are continued, theabove described process will be repeated.

Further, in the case of "f<0.5", even if all sub frames are repeatedonce, or all samples of the PCM data are repeated when no voice signal(h) is sent, the amount of the PCM data stored in the output-memory 24is made only double with respect to the amount of data in the main frame(E). To increase the amount of the PCM data in the output-memory 24according to the assigned "f" value, all or selected sub frames arerepeated twice or more, or required amount of the PCM data are repeatedrequired times when no voice signal (h) is sent. By repeating twice ormore, the required number of the samples of the PCM data can be storedin the output-memory 24, and the reproduced audio signals (e) can bereproduced at the assigned reproducing speed (f<0.5).

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description and all changeswhich come within the meaning and range of equivalency of the claims aretherefore intended to be embraced therein.

What is claimed is:
 1. A method of reproducing audio signals, comprisingthe steps of:reading a predetermined amount of original audio signalsfrom a recording medium; filtering said original audio signals toextract basic audio signals; detecting zero-cross points in said basicaudio signals; dividing said original audio signals into a plurality offrames, each frame having a starting point and a terminating point whichcorresponds to a detected zero-cross point on a time axis; repeating aselected frame; monitoring the results of said detecting step torecognize no zero-cross point sections of said basic audio signals forwhich said detecting step fails to detect zero-cross points; increasingan amount of original audio signal data for portions of said originalaudio signals which correspond to no zero-cross point sections of saidbasic audio signals recognized by said monitoring step, the amount theoriginal audio signal data is increased being based on a desiredreproducing speed; and reproducing the original audio signals inaccordance with the results of said repeating and increasing steps toslow reproducing speed.
 2. An audio player, comprising:a reading sectionfor reading a predetermined amount of original audio signals from arecording medium; a filtering section for filtering said original audiosignals to extract basic audio signals; a detecting section fordetecting zero-cross points in said basic audio signals; a processingsection for dividing said original audio signals into a plurality offrames, each having a starting point and a terminating point whichcorresponds to a zero-cross point along a time axis, and repeating aselected frame; a voice detecting section for monitoring the results ofsaid detecting section to recognize no zero-cross point sections of saidbasic audio signals for which said detecting section fails to detectzero-cross points; an increasing section for increasing an amount oforiginal audio signal data for portions of said original audio signalswhich correspond to no zero-cross point sections of said basic audiosignals recognized by said voice detecting section; and a reproducingsection for reproducing the original audio signals in accordance withthe results of said processing section and said increasing section toslow reproducing speed.
 3. The audio player according to claim 2,whereinsaid zero-cross points are included in rising parts of said basic audiosignals.
 4. The audio player according to claim 2,wherein saidzero-cross points are included in trailing parts of said basic audiosignals.
 5. The method according to claim 1, wherein said zero-crosspoints are included in rising parts of said basic audio signals.
 6. Themethod according to claim 1, wherein said zero-cross points are includedin trailing parts of said basic audio signals.